Luminaire



Jan; 14, 1964- c. E. RACKLEY EI'AL 3,117,731

LUMINAIRE 3 Sheets-Sheet 1 Filed Nov. 17, 1960 Jan. 14, 1964 c. E. RACKLEY ETAL 3,117,731

LUMINAIRE 3 Sheets-Sheet 3 Filed NOV. 17, 1960 big ig. l0

United States Patent Ofi ice 3,117,731 Patented Jan. 14, 1964 3,117,731 LUMEN Carla Racldey, VVestlalte, and Winfried Nieder-Westermann, Par-ma, @lrio, assignors to Westinghouse Electric (Iorporation, East littsburgh, Pa, a corporation of Pennsylvania Filed Nov. 17, 195i), Ser. No. 69,949 8 Claims. ((31. 240-447) This invention relates to a novel luminaire structure and more particularly to a door frame and latch structure for a lum'maire which eliminates light leaks and provides for a substantially rigid frame which will withstand the considerable wear and tear that is often incurred during the installation and maintenance thereof.

The majority of structures, particularly the recessed type, used for lighting purposes have hinged door frames for supporting shielding and light transmitting media. invariably, the luminaires of the prior art have doors which leak light through cracks in the door frame itself or leak light between t--e door frame and the housing. Such light leaks are undesirable in that they are uncontrolled and constitute wasted light emitted at various unfavorable directions and thus present an unattractive appearance to their associated luminaire.

Generally, door frames for luminaires have been made of side and end rails fastened together by either welding or by screws. Welded door frames in the first instance have many disadvantages. The first is that the heat from welding releases internal stresses in the component parts which cause the finished frame to warp. Such a warped door frame usually jams in the door opening, looks unsightly, and leaks light. The second objection is that excess metal from welding has to be ground away. Such grinding is always undesirable because regardless of the amount of care taken in the welding operation, it is always possible to see where the grinding starts and stops. The third fault is that the completed assembly is relatively expensive.

The door frames of the prior art which are assembled by screws or other fasteners rather than by welding have been quite unsatisfactory because they are usually structurally weak and leak li ht between their component parts. The present invention is related to a door frame construction which mitigates or eliminates altogether these disadvantages.

When a luminaire is installed in a ceiling the light control media is generally installed in a door or closure that is hinged to the housing for easy access to the interior of the luminaire for maintenance purposes. This generally means that the door must be opened downwardly, which requires the use of readily releasable door latches on the side of the door frame opposite from the hinges. The door latches of the prior art have been found to be awkwardly designed in that the door containing them must be lifted sli htly to disengage the latches and then dropped downwardly. If the shielding media is light in weight, the double motion is difficult. Also, many luminaires of this type are pulled too tightly into the ceiling opening by the installing personnel, so that the luminaire housing is deformed sufficiently to jam the door. The usual latches which slide or lift to unlatch do not have enough exposed area to provide a suitable finger grip either to actuate the latch or to pull the door free after the latch is operated. The novel door frame and latch mechanism described in the present invention is designed so as to overcome these dificulties.

Accordingly, one of the objects of this invention is to provide a luminaire door frame construction that substantially eliminates light leaks.

A further object of this invention is to provide a door frame for a luminaire structure which is rigid and easy to assemble.

Still another object of the present invention is to pro vide a novel door frame particularly adapted to lit with a gasketed luminaire housing.

A further object of the present invention is to provide a luminaire door frame which has side rails including extensions which seat into and seal with a gasket on the luminaire housin and which give added strength to the frame.

An additional object of the present invention is to pro vide a door frame construction for a luminaire which has a three dimensional angle corner bracket for rigidity and for firmly pulling the end and side rails thereof tightly together to eliminate open cracks therebetween and to center the shielding media longitudinally to prevent light leaks.

A further object of this invention is to provide, in the door frame of a luminaire, a hold down member which ecures the shielding media in place, covers the attaching screws and is adjustable vertically in order to secure in the frame shielding media of various thickness.

Another object of the present invention is to provide a wire tie member for the door frame in a luminaire housing to prevent the frame from spreading due to the weight of heavy shielding media and to careless handling during installation and maintenance.

Yet another object of the present invention is to provide a door frame structure which permits simple replacement of shielding media in the field by merely loosening, not removing, screw elements.

Still another object of the present invention is to provide a latch designed for the door frame of a luminaire housing which latch eliminates the need for a double motion to open the door and which presents an unusually easy linger grip element to either actuate the latch mechanism or pull the door frame free after the latch mechanism is operated.

A still further object of the present invention is to provide a latch adapted for the door frame of a luminaire and including an actuator extending through a slot in the door frame and an exposed flush plate which conceals the slot in the door frame and prevents light leaks.

Yet still another object of the present invention is to provide a latch mechanism for a luminaire door frame requiring only push-pull action to operate when it is desired to open the door frame.

Still a further object of the invention is to provide a luminaire door frame latch mechanism which is automatically adapted to snap firmly into place when the door frame is closed and which includes the safety feature that one can always tell whether or not the door is properly latched by observing the position of the flush plate.

These and other objects, features and advantages of the invention will become more apparent upon consideration of the following detailed description of a novel luminaire door frame construction and latch mechanism incorporating various components constructed in accordance with the principles of this invention when taken in connection with the following drawings, in which:

FIGURE 1 is a top plan view of a door frame con structed in accordance with the principles of the invention and having portions thereof broken away;

FIG. 2 is a partial plan view of a door frame similar to that of FIG. 1 only employing a different end section;

FIG. 3 is an enlarged cross-sectional View of the door frame of FIG. 1 taken along the reference line I lI-lll thereof and additionally including a section of a gasketed housing not shown in FIG. 1;

FIG. 4 is a somewhat enlarged partially exploded iso- 3 metric View of a section of the side rail of the door frame of FIG. 1 having portions thereof broken away;

FIG. 5 is a cross-sectional view, on a reduced scale with respect to FIG. 3, of the door frame of FIG. 1 taken along the reference line V V thereof, but additionally a portion of a housing not shown in FIG. 1;

FIG. 6 is a cross-sectional view, of the scale of FIG. 5, of the door frame of FIG. 2 taken along the reference line VI-VI thereof, but additionally including a portion of a housing not shown in FIG. 2;

FIG. 7 is a cross-sectional view, on the scale of FIG. 5, of the door frame of FIG. 1 taken along the reference line VI'I-Vll thereof;

FIG. 8 is a cross-sectional view, on the scale of FIG. 5, of the door frame of FIG. 1 taken along the reference line VEIVL1 thereof;

FIG. 9 is an enlarged partial top plan view of the lower corner of the door frame shown in FIG. 2;

FIG. 10 is a cross-sectional view of the corner shown in FIG. 9 taken along the reference line X-X thereof;

:FIG. 11 is a partial elevational view of the door frame of FIG. 1 taken along the reference line XIXI thereof;

FIG. 12 is a partial elevational view of the door frame of FIG. 2 taken a long the reference line XII-XII thereof;

FIG. 13 is an enlarged cross-sectional view of the latch mechanism and door frame of FIG. 1 taken along the reference line XX thereof but with the hold down rail removed, and additionally includes a section of a gasketed housing not illustrated in PEG. 1; and,

FIGS. 14, 15 and 16 are partial side views of the latch mechanism as shown in FIG. 13 in three operative positions, respectively.

Thus, in accordance with the principles of the present invention, there has been invented a novel door frame structure for a luminaire housing. This structure incorporates side and end rails and other supporting frame elements so shaped, as taught by the invention, that a light leak proof and substantially rigid frame structure, which is comparatively inexpensive to make and assemble, has been provided. This door frame structure includes corner bracloets which not only serve to pull the end and side rails tightly together so as to eliminate any light leaks therebetween but also serve the function of centering the light-transmitting shielding media. The door frame also includes an adjustable holding member for receiving different ones of shielding media of varying thicknesses so that it is readily adapted to any desired type of shielding media. Also included Within the scope of the present invention is a new positive snap tight latch which incorporates a push-pull mechanism for opening and closing of the door frame within the luminaire housing much more efilciently and which additionally eliminates any light leaks due to the opening in the door frame necessitated thereby.

Referring more particularly to FIG. 1, it can be seen that door frame it? of the present invention is substantially rectangular in outline as is common in present day luminaires. Of course, many of the principles of the present invention can be employed in a luminaire which is square, circular, oblong, etc. without departing from the scope thereof. The door frame it) includes side rails 12 and end rails 14- which are secured to one another by means of corner brackets 16. Across the central strand of the door frame 10 is a central web supporting element 13. This central Web 18 is employed in the relatively wide door frames wherein a pair of shielding media 19 are used in a single frame 1%. When the door frame is relatively narrower a single light-transmitting shielding media 1 extending from end to end of the door frame is normally employed and a wire supporting rod or tie 2b can be used therewith. The door frame 16 includes latch mechanisms 22 which are employed to secure the door frame in its operative closed position when desired. The door frame it} is preferably attached to the conventional housing by means of conventional hinge elements 24. All of the above mentioned parts, with the exception of the hinge elements 24', will be described in more detail hereafter.

The door frame 10" shown in FIG. 2 is substantially similar to the door frame it? shown in FIG. 1, except that it incorporate different side rails 12, end rails 14' and corner brackets 16. The other component parts therein are substantially interchangeable with the corresponding parts of the door frame It The details of this modified end section will be described later with the more detailed description of the corresponding elements of FIG. 1.

As seen more clearly in FIG. 3, the side rails 12 are substantially L-shaped with an offset or bent over portion 26 on the top of the upright leg or wall 28 thereof. The purpose of this offset is to engage a gasket so which is secured to the inner top corner in the bottom opening of the luminaire housing 32, a portion of which has been incorporated into FIG. 3 to illustrate more clearly the operation of the ofiset with respect thereto. The offset 26 and the gasket 3% thus cooperate to seal the side rails 12 of the door frame 10 with res ect to the housing 32 to prevent light leaks when the door frame is in its operative closed position. The bottom leg or wall 34 of the side rail 12 is employed to support the bottom surface of the shielding media 19.

Engaged with the side rail 12 is a generally inverted U-shaped hold down rail 36 which has an outwardly extending lower flange portion that engages the top of the shielding media 19 so as to secure it to the top of the horizontal leg 34 of the side rail 12.

The hold down rails 36 are secured to side rails 12 by means of clamping plates or clip members 38 as best shown in FIG. 4-. To assemble the hold down rails 3-6 to the side rails 12 first each clamping plate 38 (only half of one being shown in FIG. 4) is loosely engaged with the vertical leg 28 of side rail 12. This is accomplished by means of registered countersunk apertures 39 and 44 in the clamping plates 38 and vertical legs 20, respectively, being engaged by screws 42. The T-shaped slots 45 in each hold down rail 36 permits it to slip down over the clamping plates 38 enabling the back wall thereof to be frictionally engaged between each clamping plate 38 and the vertical legs 28 of the side rail 12.. More specifically, tihs engagement involves the wings 35, which constitute a considerable area, of the back wall of the hold down rail 36 being clamped by clamping plate 38 and leg 28. By tightening the screws 4-2 each hold down rail 36 is then clamped in place. Generally, the best way to obtain a secure clamping of the shielding media 19 between the lower flange 4t) of each hold down rail 36 and the leg 34 of each side rail 12 is to first rest the shielding media 1.9 on the leg 34, loosen the clamping plates 33, insert the hold down rail 36 in place by allowing the T- slots 45 to fit over clamping plates 38 and then letting it drop into position so that its flange 40 rests on the top of the shielding media 19, and then tighten the screws 4-2 which clamp both the hold down rail 36 and the shielding media in place. The hold down rails 36 are provided with vertical adg'ustability in this manner, in the direction indicated by the arrow 47 in FIG. 4, so as to be adapted to receive different thicknesses of shielding media within a certain limited range. Thus, viewing FIG. 3, when a thicker shielding media 19' is to be secured to the door frame it), the hold down rail 35 is merely dropped into its broken line position and then clamped into that position by tightening of the screws 4-2. The apertures 39 and do are countersunk to permit the fiat heads of the screws 42 to fit relatively flush with the outside face of the side rail 12 to prevent any interference between it and the housing 32.

The hold down rails 36 only engage the shielding media 19 along the hinge and latch sides 12 of the door frame it which is sufiicient to secure the shielding media 19 in place. Clips 49 and 49, FIGS. 5 and 6, in the center of L-shaped end rails 14 and 14', respectively, are employed to prevent the shielding media 19 from being knocked out of the door frame 19 before the hold down rails 36 are clamped into place. The clips 49 and 49' also aid in preventing damage to the shielding media 19 due to bending if, perhaps someone negligently pushed up on the shielding media 19 near the central end portions thereof. The clips 49 and 49' do not necessarily have to engage the shielding media 19 to perform their function, as is shown in FIGS. 5 and 6. If desired each clip 49 and 49 could be made much longer so as to practically extend the entire length of the end rails 14 or 14' and take the shape of a hold down rail if protection therealong is felt to be needed. However, it appears that the use of a clip would be sufficient for most purposes. The clips 49 and 49 are secured to the end rails by means of screws 42 in a manner similar to that employed in mounting the clamping plates 33 to the side rails 12.

"When desiring to remove or replace the shielding media 19 all that need be done is to loosen, without removing, the screws i2 along the side rails to loosen the clamping plates 38 providin for the releasing of the hold down rails 36. The hold down rails 36 are then free enough to allow jugglin of the shielding media 19 out from under them, and the clips 4-9, without the removal of any other parts. However, if desired, one or both of the hold down rails 36 can be removed by simply lifting upward thereon so as to make the release of the shielding media 19 even easier.

As is obvious from FIGS. 5 and 6 the end rails 14 and 14' do not have a bent over portion on their vertical legs comparable to portion 26 on side rails 12. This is because the particular type housing units in which the door frames 16 and id are normally used will provide a seal at their ends without the need for such a bent portion. That is, door frame 1%, shown in FIGS. 1 and 5, is adapted for use with grid type units while door frame 1%, shown in F165. 2 and 6, is adapted for use with flange type units. Both of these units are well known in the art and are illustrated in US. Fat-eat No. 2,852,663 issued to N. Stuffer et al. on September 16, 1958, entitled Luminaire and assigned to the same assignee as is the present invention. FEGS. 7 and 8 of the aforementioned patent illustrates the flange and grid type units, respectively.

Returning to the drawings of the present invention, FIG. 5 illustrates a small flexible gasket 51 secured to a grid type housing and plate 53, the gasket 51 resting against the end of the door frame it when the door is closed, to provide the light seal. FIG. 6 illustrates a lip 55 formed on the lower end of a flange type housing end plate 57. The lip 55 overlaps the upper end of the end rail 14' and cooperates with a covering plate 59 secured to the end plate 57 to prevent the escape of light from around the ends of door frame it? when in its closed position. It is the difference between the end fits of the door frame with the grid and flange type uni-ts that is responsible for the two modifications shown in FIGS. 1 and 2, respectively. That is, the door frame 10 for the flange type unit must be about one inch lower than the door frame 10 for the grid type unit.

It is also the difference in the lengths of door frames 1!} and 16 combined with the desire to use the same shielding media 3.9 for both, that makes for the difference between the corner brackets 16 and 16'. However, the simi larities between the brackets will be discussed first and where similar only reference to the brackets 16 will be made. The corner brackets 16 are right angular and are L-shaped in cross section. They are employed to sealingly secure the end ra ls 14 to the side rails 12 so as to eliminate open cracks where light could otherwise leak out between the two rails. The L-shaped cross-section of the corner brackets fits neatly within the L-shaped cross section of the side rails 12 and end rails 14- so that they can be readily screwed together by means of the screws 48 engaging registered apertures in the corner brackets and rails. As best seen in FIG. 10, the thickness of the corner brackets is relatively thin so that even though they lie on top of the bottom flange of end rails 14, the shielding media 19 will still be able to be substantially flush therewith. The corner brackets 16 are also designed to center the shielding media longitudinally within the door frame 10. The main ditference between the corner brackets 16 and 16' then is that corner brackets 16', best shown in FIGS. 9 and 10, have a wider end to fit on the wider bottom of end rail 14' and further includes the stop flange 61 which serves as an abutment for the shielding media 19 to rest against. This compensates for the longer distance between opposite end rails 14 so as to permit the same shielding media 19 to be used as is used in the shorter door frame it with the stop flange 61 serving to center the shielding media 19' as well as preventing endwise sliding thereof.

FIGS. 11 and 12 illustrate different ends of the vertical legs 28 and 28' of the side rails 12 and 12' respectively. The side rail 12 is somewhat shorter than side rail 12, due to the difference in the lengths of the door frames 10 and it), and includes a notch 59 to provide clearance for a stepped portion, not shown, in the end plate of the housing for which the door frame 10' is adapted to fit. No notch is provided in side rail 12 because the comparable end plate it is adapted to fit with does not have a stepped portion.

In door frames including only a single one-piece shielding media 19 a wire tie 2% is employed to strengthen the central portion of the door frame. As best seen n1 FIG. 7, the hold down rail 36 on each side of the frame includes a slot 52 in the top near the middle thereof through which the wire tie 24} can be engaged at its opposite ends to prevent the door frame from spreading in its middle due to the weight of the shielding media 19 and any careless handling during installation and maintenance of the door frame. The wire tie 2% has S-shaped hooked ends 54- which are engaged in cooperating slots 52 to secure the wire tie 20 at its opposite ends to the hold down rails 36 The wire tie 2% is preferably made of piano wire or of some other equivalent Wire of high tensile strength.

As seen in FIGS. 1 and 8, the central web 18 is used to provide not only rigidity for a door frame employing a pair of shielding media but also to provide a mounting means for the middle ends of the shielding media 19. The central web 18 has return flanges 56 at each opposite end thereof which are secured to the leg 28 of the side rail 12 by means of a screw 42. The web 18 is actually constructed of two L-shaped portions 58 which are secured together by welding, or by some other equivalent means, so that the bottom portion thereof forms a support for shielding media 19.

FIGS. 13 and 14 illustrate the latch mechanism 22 for the door frames 11} and 10'. The latch 22 comprises the basic components of a snap-type latch hook 74), a latch hook actuator 72, a coil spring 74 for the latch hook 7t and an opposing arm spring 76 for the actuator 72. The latch 22 is secured to the side rail 12 by means of a pivot stud 77 secured by welding or the like in aperture 79 in the side rail 12. The latch 22 is secured to the stud 77 by means of retaining ring 81 fastened in a groove, not shown, in the shank of stud '77. If desired, a spacer 83 can be supported by the stud 77 to space the latch mechanism 22 a given distance from the side rail 12. The latch hook it? and the latch hook actuator 72 are rotatable with respect to one another about the stud 77. The actuator 72 has an arm or extension 73 that extends through an opening 78 in the bottom 34 of the side wall 12 and has integrally attached thereto a flush grip plate 3i When in its operative closed position as shown in FIGS. 13 and 14, the hush plate so serves to conceal the slot 78 and prevent light leaking therethrough because it is of a size to entirely cover the opening '78. The actuator spring '76 has its lower end biased against the top surface of the bottom leg 34, is wrapped around the stud '77 and is engaged by the projection 83 in order to biasedly secure it to the actuator 72. The actuator 72 carries a hook or catch 84 which is adapted to engage the notch portion or lip 86 of the latch hook 743 as will be explained more completely in the description of H68. 15 and 16. The latch hook 7% extends outwardly through an opening 38 in the luminaire housing 32 having its very end 90 of the hook '70 engaging the top flange of the door opening in the housing 32 so as to firmly seat the offset 26 of the side rail 12 against the gasket thus providing for the aforementioned light leak seal between the housing 32 and the door frame it). This firm engagement is caused by the spring 74 being engaged upon the downwardly extending projection $2 of the latch hook 713. The bottom of the latch hook spring 7-4 is engaged against the upwardly extending projection 94 on the bottom of the leg 34' to place the latch hook spring 74 in compression.

It can readily be seen that the engagement of the latch hook it? with the housing 32 is merely accomplished by pushing the nose $6 of the latch hook 719 up through the opening 88 where it will be biased backwardly until the hook end 9h clears the opening 38 where it will then snap into place over the top flange of the door opening in the housing 32. In other words, to close the door frame it is merely pushed into the door opening of the housing and the latch hook 70 will snap firmly into place through the opening 88. If there should happen to be mechanical interference such that the latch hook 7% does not snap readily into place, it may be forced into a locking position by merely pushing against the fiush plate 89.

To open the door frame it it is necessary to first push sideways against the flush plate 36. By pushing sideways against the fiush plate 39 in a lateral direction, as indicated by the arrow 38 of FIG. 14, the actuator '72 will be pushed downwardly into the position shown in FIG. 15. The portion of the actuator 72 shown exposed in FIG. can then be gripped between the thumb and forefinger and pulled downwardly into the position shown in FIG. 16. This downward pull operates the latch hook 76 so that the end 9% thereof is freed of the housing 32, through the opening 88, so that in one motion the downward pull actuated the latch hook 7G and pulled the door frame it) free of the housing 32. When this downward force is applied, the catch 84 of the actuator 72 engages the notch as of the latch hook 7%, and thereby pulls the latch book 70 backward out of its engaged position with the housing 32.

As a safety feature inherent in the construction of the latch 22, it can always be told whether or not the door is properly latched by observing the position of the flush plate 3 That is, if the flush plate Sit is against the bottom leg 34 of the side rail 12, the door 19 is properly latched. But, if the flush plate 89 is away from the side rail 12 the frame is not properly latched. This safety feature can prevent many accidents when installation or maintenance of a luminaire employing a door frame 10 is required.

Thus, there has been disclosed a door frame structure for a luminaire which is both rigid and non-warpable, prevents light leaks, and is easily installed and operated. The component parts of the door frame make it readily adaptable to a luminaire housing employing a gasket to seal the door frame to the housing. The door frame is adapted to be secured on one longitudinal edge by means of hinges and on the other by a novel spring latch mechanism. The latch mechanism provides a relatively tight sealed lit for the door frame with respect to the housing and also presents a mechanism which is readily releasable and provides a seal so that light cannot leak through the opening in the door frame necessitated by the latch mechanism. The latch mechanism inherently incorporates the safety feature that it is obvious from the position of the latch mechanism whether the door frame is securely fastened in its operative position or not.

Since it is obvious that the invention can be embodied in other forms and constructions within the spirit and scope of the invention, as would be apparent to one skilled in the art, it is to be understood that the particular forms shown are but a few of such embodiments. Accordingly, with various'modifications and changes being possible, the invention is not limited in any way with respect thereto. Moreover, it is to be understood that certain features of the invention can be employed without a corresponding use of other features thereof.

Accordingly, what is claimed as new is:

1. A door frame for a luminaire housing, said frame comprising opposite side rails and opposite end rails, releasable connecting means for sealingly connecting said rails together so as to form corners of said frame, said side rails being of a generally L-shaped cross section having upright legs and bottom legs with the bottom legs thereof extending towards their opposite side rail, said bottom legs forming a support for shielding media contained in said frame, a hold down member having apertured walls presenting wing portions on one wall thereof, slots adjacent the apertures and contiguous therewith, said slot being located in another transversely displaced top wall of said hold down member, clamp means insertable through said slots frictionally engaging at least one of said wings to the upright legs of said side rails in any one of a plurality of positions for adiustably securing shielding media of differing thicknesses within said frame, and a bent over portion integral with the top of the upright leg of said side rails, the bent over portion of said side rails and the top of the upright leg of said end rails being adapted for cooperation with mating means on said housing for preventing light leaks between said housing and said frame when in its closed operative position.

2. A door frame for a luminaire housing, said frame comprising opposite side rails and opposite end rails, releasable connecting means for sealingly connecting said rails together so as to form corners of said frame, said side rails being of a generally L-shaped cross section having upright legs and bottom legs with the bottom legs thereof extending towards their opposite side rails, said bottom legs forming a support for shielding media con tained in said frame, a generally inverted U-shaped hold down member with one arm thereof engaging the upright leg of each side rail, the other arm of said hold down member spaced inwardly toward the opposite side rail, a flange integral with said other arm and extending inwardly to the extent that its free inner end is generally coextensive with the free inner end of the bottom leg of said side rail, said flange and said bottom leg serving as means for clamping a light-transmitting shielding media therebetween, clip means for adjustably and releasably securing said hold down member to said side rail, said hold down member being adapted to alternatively clamp shielding media of different thicknesses to said frame and provide for the ready release of the same.

3. A door frame for an open bottomed luminaire housing, said frame comprising opposite side rails and opposite end rails, releasable connecting means for sealingly connecting said rails together so as to form corners of said frame, said side rails being of a generally L-shaped cross section having an upright leg and a bottom leg with the bottom legs thereof extending towards their opposite side rail, said bottom legs forming a support for shielding media contained in said frame, a generally inverted U-shaped hold down member with one arm thereof located generally adjacent the upright leg of each side rail, the other arm of said hold down member spaced inwardly toward the opposite side rail, a flange integral with said other arm and extending inwardly to the extent that its free inner end is generally coextensive with the free inner end of the bottom leg of said side rail, said flange and said bottom leg serving as means for clamping a light-transmitting shielding media therebetween, said hold down member having spaced T-shaped slots formed in its eight portion and said one arm, clips located at spaced positions along the upright leg of said side rail so as to mate with each of said slots, screw means threadedly engaged through registered apertures in said clips and said upright le to releasably clamp them together, said one arm of said hold down member being at least partially engaged between said clips and said upright, said slots providing for passage of said screws through said hold down member, whereby tightening of said screws serves to clamp said hold down members to said side rails and to clamp said shielding media between said hold down members and said side rails and whereby loosening of said screws permits ready removal of said shielding media from said frame.

4. A door frame for a luminaire housing, said frame including opposite side rails, hinge means located on one of said side rails, at least one latch located on the other one of said side rails, said other side rail including at least an upright wall and a bottom wall in a generally L-shaped configuration, said latch comprising a spring biased hook extending beyond the top of said upright wall for engagement with said housing through an aperture therein, a spring biased actuator, stud means pivotally securing said hook and said actuator coaxially to said upright wall, catch means integral with said actuator for engaging said hook in order to release said hook from engagement with said housing, said actuator catch means being angularly displaced from the engaging portion of said hook, said actuator including an extension protruding through an openin in said bottom wall, a flush plate forming part of said extension at its protruding end and being of a size to cover the opening in said bottom wall, whereby partial rotation of said flush plate is effected with minimal effort to aiford a better grip prior to the catch means engaging said hook for disengagement of said door frame, said flush plate serving as a finger grip for actuating said actuator as well as serving to close the opening in said bottom wall to prevent light leaks when said frame is in its closed operative position.

5. A door frame for a luminaire housing, said frame including opposite side rails, hinge means located on one of said side rails, at least one latch located on the other one of said side rails, said other side rail including at least an upright wall and a bottom wall in a generally L-shaped configuration, said latch comprising a hook member, a spring for biasing said hook member against said bottom wall and extending beyond the top of said upright wall for engagement with said housing through an aperture therein, a notch formed in said hook, an actuator, stud means pivotally securing said hook and said actuator conxially to said upright wall, catch means integral with said actuator for engagement in the notch in said hook, said actuator including an extension protruding through an opening in said bottom wall, a flush plate forming part of said extension at its protruding end and being of a size to cover the opening in said bottom wall, means for biasing said actuator against both said hook and said bottom wall so that said flush plate is held flush against said bottom Wall when said hook is engaged with said housing, said catch means being angularly displaced trom the engaging portion of the notch in said hook so as to be free in said notch until said flush plate is pulled a short distance from said bottom wall but being engaged with said hook against the biasing action of its spring after said short distance is traveled, said flush plate serving as a grip for actuating said actuator to disengage said hook from the housing as well as serving a cover for the opening in said bottom wall when said door frame is in its operative closed position.

6. A door frame for a luminaire housing, said frame comprising opposite side rails and opposite end rails, substantially right angular corner brackets having a crosssection generally similar to but slightly smaller than that of said side and end rails, said corner brackets connecting adjacent ends of said side and end rails by resting up against the inner surfaces of said side and end rails at the corners formed by said adjacent ends, and releasable means for securing said corner brackets to said side and end rails so that cracks are substantially eliminated at the juncture of said adjacent ends, hinge means located on one of said side rails, at least one latch located on the other one of said side rails, said latch comprising a hook member, means for biasing said hook against said bottom wall and extending beyond the top of said upright Wall for engagement with said housing through an aperture therein, a notch formed in said hook, an actuator, stud means pivotally securing said hook and said actuator coaxially to said upright wall, catch means integral with said actuator for engagement in the notch in said hook, said actuator including an extension protruding through an opening in said bottom wall, a flush plate forming part of said extension at its protruding end and being of a size to cover the opening in said bottom wall, means for biasing said actuator against both said hook and said bottom wall so that said flush plate is held flush against said bottom wall when said hook is engaged with said housing, said catch means being angularly displaced from the engaging portion of the notch in said hook so as to be free in said notch until said flush plate is pulled a short distance from said bottom wall but being engaged with said hook against the biasing action of its spring after said short distance is traveled, said flush plate serving as a grip for actuating said actuator to disengage said hook from the housing as well as serving a cover for the opening in said bottom 'wall when said door frame is in its operative closed position.

7. Ina luminaire housing, a door frame and a shielding medium, said frame comprising rail members, an elongated hold down member holding down said shielding medium, said hold down member maintaining substantially continuous contact with said shielding medium along a major portion of the periphery of said shielding medium, said hold down member having a wall portion and a top rail portion, an aperture in said wall portion, a slot in said top rail portion, said slot positioned adjacent the aperture in said wall portion and opening into said aperture, wing portions in said wall portion formed by said slot and said aperture, clamp means releasably secured within said slot and frictionally securing at least one of said wing portions to one of said rail members, whereby said hold down member can be adjusted to accommodate shielding media of varying thickness by releasing said clamp member.

8. A door frame for a luminaire housing, said frame including opposite side rails, hinge means located on one of said side rails, at least one latch located on the other one of said side rails, said other side rail including at least an upright wall and a bottom wall in a generally L-shaped configuration, said latch comprising a hook biased by a spring and pivotally secured to said upright wall and extending beyond the top of said upright wall for engagement with said housing through an aperture therein, said spring biasing said hook into engagement with said housing, actuating means adjacent said hook and pivotally secured to said upright wall for releasing said hook from an engaged position in opposition to the biasing force exerted by the hook spring, said actuating means including an extension protruding through an opening in said bottom wall, a flush plate forming part of said extension at its protruding end and constituting a finger grip for said actuating means, said flush plate overlapping and closing the opening in said bottom wall to prevent light leaks, the hook-engaging portion of said actuating means being angularly displaced when said actuating means is in a closed position from the corresponding engaging portion of said hook by an amount suflicient to permit initial angular displacement of said actuating means before said actuating means engages said hook, whereby initial movement of said actuating means is accomplished with minimal effort.

(References on following page) ReEeremes Citefi in the file of this patent UNITED STATES PATENTS Kiesel Feb. 11, 1903 Bristol Apr. 27, 1926 5 Goddard et 21 Dec. 19, 1933 Anderson J'uly 23, 1940 Beals July 28, 1942 Kaeppel May 29, 1951 Scarborough July 10, 1951 10 Goldbsrg July 10, 1951 Gurney Aug. 21, 1951 12 Stubbs Mar. 4, 1952 Dunna et a1. Apr. 27, 1954 Smith May 31, 1955 Stuffer et a1 Sept. 16, 1958 Sorenson 3- Feb. 23, 1960* Slater et a1 Mar. 15, 1960 Pascucci Ian. 30, 1962 FOREIGN PATENTS France Jan. 9, 1925 Great Britain Aug. 10, 1944 

8. A DOOR FRAME FOR A LUMINAIRE HOUSING, SAID FRAME INCLUDING OPPOSITE SIDE RAILS, HINGE MEANS LOCATED ON ONE OF SAID SIDE RAILS, AT LEAST ONE LATCH LOCATED ON THE OTHER ONE OF SAID SIDE RAILS, SAID OTHER SIDE RAIL INCLUDING AT LEAST AN UPRIGHT WALL AND A BOTTOM WALL IN A GENERALLY L-SHAPED CONFIGURATION, SAID LATCH COMPRISING A HOOK BIASED BY A SPRING AND PIVOTALLY SECURED TO SAID UPRIGHT WALL AND EXTENDING BEYOND THE TOP OF SAID UPRIGHT WALL FOR ENGAGEMENT WITH SAID HOUSING THROUGH AN APERTURE THEREIN, SAID SPRING BIASING SAID HOOK INTO ENGAGEMENT WITH SAID HOUSING, ACTUATING MEANS ADJACENT SAID HOOK AND PIVOTALLY SECURED TO SAID UPRIGHT WALL FOR RELEASING SAID HOOK FROM AN ENGAGED POSITION IN OPPOSITION TO THE BIASING FORCE EXERTED BY THE HOOK SPRING, SAID ACTUATING MEANS INCLUDING AN EXTENSION PROTRUDING THROUGH AN OPENING IN SAID BOTTOM WALL, A FLUSH PLATE FORMING PART OF SAID EXTENSION AT ITS PROTRUDING END AND CONSTITUTING A FINGER GRIP FOR SAID ACTUATING MEANS, SAID FLUSH PLATE OVERLAPPING AND CLOSING THE OPENING IN SAID BOTTOM WALL TO PREVENT LIGHT LEAKS, THE HOOK-ENGAGING PORTION OF SAID ACTUATING MEANS BEING ANGULARLY DISPLACED WHEN SAID ACTUATING MEANS IS IN A CLOSED POSITION FROM THE CORRESPONDING ENGAGING PORTION OF SAID HOOK BY AN AMOUNT SUFFICIENT TO PERMIT INITIAL ANGULAR DISPLACEMENT OF SAID ACTUATING MEANS BEFORE SAID ACTUATING MEANS ENGAGES SAID HOOK, WHEREBY INITIAL MOVEMENT OF SAID ACTUATING MEANS IS ACCOMPLISHED WITH MINIMAL EFFORT. 